Apparatus for and method of forming multiple simultaneous electronically scanned beams using direct digital synthesis

ABSTRACT

The apparatus/method according to the present invention accomplishes a reduction in the total number of direct digital synthesizers (DDSs) needed for use in electronically scanned antenna array to generate multiple simultaneous radio frequency (RF) beams. The apparatus includes, inter alia, a multi-beam forming synthesizer, a plurality of DDSs, a corresponding plurality of amplifiers all operatively connected to a plurality of radiating elements of the antenna array. This arrangement uses a single DDS per radiating element. Each DDS uses a composite amplitude, phase and frequency information computed by the multi-beam forming synthesizer to create the proper waveform for driving the antenna array, and accordingly, generating the desired multiple simultaneous RF beams.

RELATED APPLICATION

[0001] This Patent Application claims the benefit of U.S. ProvisionalApplication Serial No. 60/331,291 filed on Nov. 14, 2001.

BACKGROUND OF THE INVENTION

[0002] 1.Field of the Invention

[0003] The present invention relates to an improved apparatus (hardwarearrangement) and algorithm that employs a direct digital radio frequencysynthesizer to generate and transmit multiple simultaneous radiofrequency (RF) beams, which can be electronically scanned.

[0004] 2. Description of the Prior Art

[0005] In the past, a number of methods and apparatus have been used togenerate electronically scanned radio frequency beams using arrayelements. These methods include both analog beamforming and digitalbeamforming techniques that are applied to transmit array antennas asdiscussed in the references [1,2]. By the principal of superposition itis possible to apply same frequency signals to each of N radiatingelements so that the summation of same frequency signals at a point inthe field of the elements forms a single beam, which can beelectronically scanned by introducing a relative timing or phase delayat each of the elements. Those skilled in the art know that for example,the aperture size of an array antenna can be increased by increasing thetotal number of radiating elements N so that a sufficiently narrow beamwidth can be achieved so as to direct RF energy in a specified directionwith a desired beam width. It is possible to digitally generate RFsignals using an apparatus referred to a direct digital synthesizer(DDS) and as described in the references [3,4,8,9] for example. SuchDDSs produce RF signals with an output that is determined by digitalcontrol signals, which may include clock, amplitude, frequency and phasecontrol signals. Using a DDS it is therefore possible to generate a RFwaveform which is defined by the digital control signals.

[0006] It is possible, therefore, to use a DDS to generate a digitallyformed beam that can be electronically scanned with digital controlsignals. Prior art methods for digitally forming RF beams using a DDSare disclosed, for example, in references [6,6a,7]. In the prior art, anarchitecture produces a single RF beam with N element chains, where anelement chain consists of at least a DDS, digital control signals, and aradiating antenna element. The digital control architecture, amplitude,phase and frequency are all provided in parallel to each of theelements, thus facilitating a means of controlling modulation of theproduced waveform. A clock signal is distributed to DDS circuits inorder to establish a timing reference useful in synchronizing multipleDDS circuits. Proper phasing of the RF waveforms provided to each of theradiating elements within the array permits the beam to beelectronically scanned to a desired pointing direction. The limitationof the architecture of the prior art is that it produces only a singlebeam per beamformer and array, using the N elements.

[0007] It is often desirable to radiate more than one RF beam, whereeach beam or set of beams may have a different center frequency andmodulation using the same array aperture as disclosed in references[1,2,5,5a]. However, the existing prior art method for generating Mmultiple simultaneous beams from the same aperture is to the use theprinciple of superposition to sum signals prior to driving the radiatingelement, so that it requires M beamforming units to combine the signals.As disclosed in references [6,6a,7], one DDS circuit is required forevery radiating element in order to produce a single RF beam. Thus, Inorder to handle M different information signals that are to be formedinto M different independent RF beams, M DDS circuits are required perradiating element in the antenna array. The synthesized RF signals for agiven radiating element (or subarray) are summed using an RF combiningnetwork and applied to the radiating element. The RF signals areradiated and by superposition form the desired RF beams. Therefore,prior art systems, would require N×M total DDS circuits to form M beamshaving the same beamwidth as the single beam system described above.Thus, there is a need in the prior art to reduce the hardwarerequirements for a DDS electronically scanned array system that isconfigured to form multiple independent beams in an improved manner.

OBJECTS OF THE INVENTION

[0008] Accordingly, a principal object of the present invention is toconfigure an apparatus and create a method that efficiently andoptimally produces multiple simultaneous RF beams, i.e., M beams, whichare independently electronically scanned and can be easily defined insoftware.

[0009] A corollary of the above object is to reduce the number of DDScircuits needed from N×M to N, while maintaining the effective aperturesize used to generate each of the M independently pointed beams whichmay contain independent frequency and/or modulation information.

[0010] A further object of the present invention is to reduce the needfor RF combining circuits in order to generate the multiple simultaneousRF beams.

[0011] Another object of the present invention is to generate additionalRF beams, which can be used to transmit radar, communications, or otherinformation with a minimal increase in hardware.

[0012] Yet still another object of the present invention is to improvethe capacity to generate additional RF beams by defining in software thenumber, frequency, and modulation of the RF beams thereby providingfurther improvement in system flexibility.

SUMMARY OF THE INVENTION

[0013] In accordance with the above stated objects, other objects,features and advantages, the apparatus of the present invention isconfigured to generate multiple simultaneous RF beams using a minimalnumber of DDS circuits and related hardware. This increase in the numberof RF beams in an antenna array system permits an increase in throughputof radar, communications and other signal information without increasingthe DDS circuits necessary, and, accordingly, the number of associatedradiating elements in the antenna array system needed.

[0014] The essence of the invention is in the use of digital signalprocessing to combine signals digitally so that the same DDS perradiating element can produce the superposition of multiple waveforms tocreate the multiple beams. The digital control signals that are appliedto each DDS consist of amplitude, phase, and frequency signals, whichare parameters that can be defined in software. The apparatus and methodof the present invention are improvements over the prior art since theyrequire less circuitry and provide the capacity to reconfigure thenumber of RF beams without an increase in hardware.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The previously stated objects, other objects, features andadvantages of the present invention will be more apparent from thefollowing more particular description of the preferred embodiments,taken in connection with the accompanying drawings, in which:

[0016]FIG. 1 is a system block diagram that shows user definedinformation at its input to be transmitted input and the formation ofmultiple simultaneous RF beams at its output for carrying theinformation to be transmitted;

[0017]FIG. 2 is a block diagram representation of a direct digitalsynthesizer (DDS) having digital control signal inputs and RF signaloutputs;

[0018]FIG. 3 is a block diagram of the invention showing the signalinputs, frequency, amplitude, phase and pointing angle for each of Mbeams applied to a multibeam forming synthesizer and the apparatusarrangement connecting the digital control signal to the DDSs of FIG. 2;and

[0019]FIG. 4 is a functional flow diagram of the operational blocks ofthe multibeam forming synthesizer of FIG. 3, showing the computingfunctions thereof in accordance with the operation of the presentinvention.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020]FIG. 1 shows a top-level diagram of a multiple simultaneous beamsystem 10 in accordance with the present invention. A user of theinvention defines information content to be transmitted on each of theRF beams 1-M (e.g., 1 through M, where M is the total number of RF beamsto be transmitted). This information are time samples selected from thegroup of frequency, modulation information, digital data, and pointingdirections which are processed by a beam modulation and pointingcomputer 12. The beam modulation and pointing computer 12 converts theinformation content to be transmitted in the beam to a set ofstandardized format digital control signals for each of the 1-M beams.For the m-th beam the modulation control signals are written as signalamplitude B_(m), frequency ω_(m), phase φ_(m), and beam pointingdirection θ_(m). The modulation control signals containing amplitude,phase, frequency and pointing information are inputted to the multi-beamdigitally scanned array apparatus 14, which is operatively connected to1-N (e.g., 1 through N, where N is the total number of array radiatingelements) radiating elements 16 so as to simultaneously generate theindependent scanned RF beams 1-M, aforementioned. At positions locatedin the field of view for the array radiating elements, the 1-M multiplesimultaneous independent beams are formed by superposition of thesignals defined by the modulation control signals and generateddigitally by use of the direct digital synthesizers internal to themulti-beam digitally scanned array apparatus 14 and described in FIGS.2, 3 and 4.

[0021]FIG. 2 shows a functional block diagram of a Direct DigitalSynthesizer (DDS) 18 used in the invention internal to the multi-beamdigitally scanned array apparatus 14, which is used to digitally form amodulated RF sinewave signal of the form A_(n)(t)cos[ω_(o)(t)t+Φ_(n)(t)] at its output. The modulation inputs to the DDS18 are amplitude A_(n)(t), frequency ω_(o)(t), and phase modulationΦ_(n)(t), where the parameter t denotes time because the digital controlmodulation inputs can vary over time. These inputs are in the form ofdigital words, and the output of the DDS 18 is an analog, sinusoidalvoltage of the specified frequency, phase and amplitude as depicted.

[0022] Still referring to FIG. 2, those skilled in the art will knowthat DDS 18 may have an additional clock pulse input signal (not shown)which can be used to provide timing synchronization of a plurality ofDDSs 18 so that multiple coherent synchronized signals, which arecoherently summed, are produced. For purposes of the present invention,DDS 18 comprises a phase accumulator 20, a sine/cosine lookup table 22,a digital-to-analog (D/A) converter 24, and a filter 26. Fundamentally,the DDS 18 operates by taking the frequency word at its input andaccumulating it in the phase accumulator 20. This accumulation forms aphase angle. To this angle is added the phase input to the DDS 18 at anadder 28 to obtain a sum total phase. This composite angle is theninputted to the sine/cosine look up table 22. The output of thesine/cosine look up table 22 is the sine or cosine of the angle,representing samples of an RF sine-wave signal. This value is thenamplitude modulated (multiplied) in the multiplier 30 by the amplitudeinput to the DDS 18, and the resultant digital word is converted to ananalog voltage by the D/A converter 24. The output of the D/A converter24 is then filtered in filter 26 to smooth it and eliminated aliasfrequencies. This becomes the RF signal output of the DDS 18 whichcontains amplitude, frequency and phase information relative to acoherent clock or reference signal.

[0023]FIG. 3 shows, in block diagram form, the multibeam digitallyscanned array apparatus 14 for forming multiple simultaneouselectronically scanned beams, according to the present invention. Themultibeam digitally scanned array apparatus 14 comprises a multibeamforming synthesizer 32, a plurality of DDSs 18, a plurality ofamplifiers 34 and a plurality of radiating elements 16. This arrangementuses a single DDS 18 per radiating element 16 to form multiplesimultaneous independent beams, which is an important and novel aspectof the present invention. This is realized because of the functionalityof the multibeam forming synthesizer 32 as coupled to the DDS for eachelement in accordance with the architectural layout of invention. Themultibeam forming synthesizer 32 inputs are the amplitude, frequency,phase, and beam directions for each of the various signals to becontained in each of the beams. The outputs of the multibeam formingsynthesizer 32 are superposition of the modulation control signals andcontain the composite of amplitude, phase, and frequency signal that isused to control a single DDS per radiating element to form multiplesimultaneous independent RF beams in the filed of view of the antennaarray. These quantities can all vary in time, and in fact, the variationin time of the amplitude, frequency, or phase represents the importantinformation in each individual signal. Therefore a clock is provided tothe multibeam forming synthesizer 32 in order to provide synchronizationand timing that is required to compute the time sampled digital controlsignals coupled to each 1-N DDSs 18.

[0024] Referring to FIGS. 3 and 4 as viewed concurrently, whenmodulation control signals are applied to the multibeam formingsynthesizer 32 it decides if a new clock signal is present as indicatedby decision block 36. If yes, then the multibeam forming synthesizer 32computes the phase shift for each signal needed for each radiatingelement 16 to point that signal in the required direction as indicatedby processor block 38. Next, the multibeam forming synthesizer 32computes the carrier offset frequencies for each of those signals asindicated by processor block 40. The in-phase and quadrature componentsfor each signal are then computed as indicated by processor block 42.Finally, the resultant output amplitude and phase for input to each ofthe DDSs 18 is computed by the multibeam forming synthesizer 32 asindicated by processor block 44. In the implementation of process blocks38, 40, 42, 44 it is important to note that the multi-beam formingsynthesizer 32 computes time sample representation of a baseband (e.g.,composite) signal containing the superposition of all information withinthe M beams, and therefore a minimum sampling rate of at least twice thesaid information bandwidth (e.g., the Nyquist sampling criterion) isrequired.

[0025] Still referring to FIGS. 3 and 4 as viewed concurrently, and toreiterate, the multibeam forming synthesizer 32 causes the information,i.e., the modulation control signals, at its input to be combined intoone signal so that only one DDS 18 per radiating element 16 is required.As shown in FIG. 3, a common clock signal is coupled to each of the DDSs18 to provide timing for synchronization of the plurality of DDSs 18 andthe radiating elements 16 needed to obtain coherent signals necessaryfor beamforming.

[0026] When reviewing the following examples of implementing theinvention in hardware and software by algorithmic representation, referto FIGS. 3 and 4 as viewed concurrently.

EXAMPLE 1

[0027] There are a number of ways to implement the digital processingfunctions of the multibeam forming synthesizer 32 of the presentinvention. For example, any of the serial or parallel processing methodscurrently employed in commercially available digital computers would besufficient. Serial processing computers can perform the processingalgorithms sequentially and then distribute the results in serialfashion to each of the 1-N DDSs 18. Parallel processing can beimplemented by using a single processor at each one of the 1-N of DDSs18 to implement the digital calculations for each DDS 16 in parallel.Various configurations that combine both serial and parallel processingcan also be implemented. Those skilled in the art recognize thatparallel processing provides a processing speed advantage forcalculations that can be implemented in parallel (compared to serialprocessing), thus providing improved and streamlined digital processing.

EXAMPLE 2

[0028] Another embodiment for the multibeam forming synthesizer 32 is toimplement the digital processing functions in re-configurable logic,such as, for example, a field programmable gate array (FPGA). Such FPGAscan perform software programmable executions of hardware logic, andtherefore can be reconfigured to optimize the processing algorithm,based on, for example, the number of beams, type of modulations etc.Such an embodiment provides added flexibility in the capacity of thepresent invention to be programmed in software.

[0029] Following each DDS 16 is an amplifier 34 having a bandwidthsuitable to amplify and pass the RF signal generated by the DDS 16.Those skilled in the art are aware that the use of the amplifier 34 andbandpass filters 24 of FIG. 2 is optional and dependent upon the desiredamount of energy and spectral purity of the signal to be radiated by theantenna array.

EXAMPLE 3

[0030] The carrier offset frequency, ω_(o), is computed by themulti-beam forming synthesizer 32 for 1-M beams and can be chosen inmany different ways. For example, it could be selected as the mean ofthe input signal frequencies given by the equation $\begin{matrix}{\omega_{o} = {\frac{1}{M}{\sum\limits_{m = 1}^{M}\quad {\omega_{m}.}}}} & (1)\end{matrix}$

[0031] For those skilled in the art it is obvious that ω_(o) could beselected, for example, at the lower or upper frequency band edges of thecomposite signal to be formed by the DDS 16. In fact, the only practicalrestriction on ω_(o) is that it must be selected so that it is a validfrequency control word over the usable frequency of operation for theDDS 18.

EXAMPLE 4

[0032] The RF signal output from the amplifier 34 is coupled to aradiating element 16. For purposes of the present invention, theradiating element 16 is usually an individual antenna element consistingof, for example, patches, spirals, slots, dipoles or horn type antennas.Two or more radiating elements 16 can be used to form a beam that may beelectronically scanned. The criteria for radiating element 16 is that itnormally provides a radiation pattern, or main lobe which covers theextent of the field of view scanning range for the array.

EXAMPLE 5

[0033] The computation of phase shifts for steering of RF beams is shownbelow. The beams are electronically scanned by selecting a phase shiftΔφ_(mn) for each corresponding n-th element and the m-th beam in orderto provide a phase tilt in the energy radiated from the radiatingelements 16. For example, a linear array could accomplish beam steeringby applying a linear phase tilt given by $\begin{matrix}{{\Delta\varphi}_{mn} = {\frac{d\quad \omega_{m}}{c}\left( {n - 1} \right)\quad \sin \quad \theta_{m}}} & (2)\end{matrix}$

[0034] where d is the spacing between elements, c is the velocity oflight (c 3≈10⁸ meters per second), and θ_(m) is the pointing angle forthe m-th beam relative to the perpendicular of the linear array. Forthose skilled in the art, it is obvious that one can utilize techniquesfor positioning arrays of radiating elements 16, for example, in aplanar, circular or conformal displacement of radiating elements 16, atwhich a different equation than above would be used to compute phaseshifts needed for electronically scanning the beam.

EXAMPLE 6

[0035] Consider 1-M beams operating at different frequencies and withdiffering amplitudes and phases as aforementioned. At the n-th one ofthe radiating element 16 the composite signal is the superposition ofsignals for each beam given by s_(1n)+s_(2n)+ . . . +s_(Mn), where eachof the signals for each beam are defined as:

RF beam 1 is of the form s _(1n) =B ₁ sin[ω₁ t+φ ₁+Δφ_(1n)]  (3a)

RF beam 2 is of the form s _(2n) =B ₂ sin[ω₂ t+φ ₂+Δφ_(2n)]  (3b)

[0036] 

[0037] 

[0038] 

RF beam M is of the form s _(Mn) =B _(M) sin[ω_(M) t+φ_(M)+Δφ_(Mn])  (3c)

[0039] In this embodiment the superposition of each of the RF beamsignals is placed in the standardized form of A_(n)(t)cos[ω_(o)(t)t+Φ_(n)(t)] by using the following in-phase I_(n) andquadrature Q_(n) definitions of the signals for the n-th to be radiatedby the radiating element 16. The amplitude control coupled to the n-thradiating element 16 is given by $\begin{matrix}{{A_{n} = \left( {I_{n}^{2} + Q_{n}^{2}} \right)^{1/2}}{Where}{I_{n} = {\sum\limits_{m = 1}^{M}\quad {B_{m}{\cos \left\lbrack {{\left( {\omega_{m} - \omega_{o}} \right)t} + \varphi_{m} + {\Delta\varphi}_{mn}} \right\rbrack}}}}{Q_{n} = {\sum\limits_{m = 1}^{M}\quad {B_{m}{\sin \left\lbrack {{\left( {\omega_{m} - \omega_{o}} \right)t} + \varphi_{m} + {\Delta\varphi}_{mn}} \right\rbrack}}}}} & (4)\end{matrix}$

[0040] The phase control coupled to the n-th radiating element 16 ascomputed by the multibeam forming synthesizer 32 is given by thefollowing

Φ_(n) =arctan(Q _(n) /I _(n))  (5)

[0041] With the control signals A_(n), Φ_(n) and ω_(o) applied tocontrol the n-th DDSs 18 the signal coupled to the n-th radiatingelement 16 becomes: A_(n)(t)cos[ω_(o)(t)t+Φ_(n)(t)]. The RF signalgenerated by the 1-N DDSs 18 and radiated by the 1-N radiating element16 which form the antenna array and provides multiple independentsimultaneous beams as in FIG. 1. Each of the 1-M RF beams shown in FIG.1 have an RF signal with modulation and pointing direction as defined byspecified amplitude, phase, frequency and pointing direction as given inequations (1) through (5).

EXAMPLE 7

[0042] Those skilled in the art are aware that electronically scannedarray systems can employ multiple clock and timing distributionsubsystems. Timing and synchronization are important considerations forthe generation and distribution of control and RF signals required toproduce coherent signals at radiating elements 16 in order to form themultiple simultaneous RF beams as depicted in FIG. 1. The multiplesimultaneous beam system 10 as reduced to practice likewise employs amaster clock (or timing signal) to provide synchronization and timingcontrol for the beam modulation and pointing computer 12, the multibeamdigitally scanned antenna array apparatus 14, and components therein.The clock signal or a multiple thereof for example as shown in FIG. 3 iscoupled to each of the 1-N DDS 18 and to the multibeam formingsynthesizer 32 so as to provide coherent synchronization for each of theRF signals generated by the DDS 18 and coupled to the radiating element16. Those skilled in the art are aware that the timing andsynchronization clock frequency for the DDS 18 must satisfy a timesampling rate referred to as the Nyquist Criterion which would normallybe at least twice the RF frequency output of the 1-N DDS 18. Similarly aclock is required by the multi-beam forming synthesizer 32 that is atleast twice the bandwidth of the information contained in the RF beams.Therefore the multi-beam forming synthesizer 32 performs iterations at afrequency that is at least twice the bandwidth of the information to begenerated by the composite control signals coupled to the DDSs 18, andtherefore requires a clock signal therein of. For the purposes of thisinvention range of RF frequencies would include microwave frequencieswhich are generally between 1-40 GHz. Also, for the purposes of thisinvention the bandwidth of signal to be generated by the 1-M RF beamsrange from 10 MHz to about 4 GHz as dependent on the rate the DDS canaccept digital control signals for modulation.

[0043] To those skilled in the art, many modifications and variations ofthe present invention are possible in light of the above teachings. Itis therefore to be under stood that the present invention can bepracticed otherwise than as specifically described herein and still bewithin the spirit and scope of the appended claims.

REFERENCES

[0044] [1] R. J. Mailloux, Phased Array Antenna Handbook, Artech House1994.

[0045] [2] H. Steyskal, “Digital Beamforming at Rome Laboratory”, pp.100-126, Microwave Journal, February 1996.

[0046] [3] J. Matsui, et al., “InP DHBT Ultra High Speed Direct DigitalSynthesizer”, GOMAC-2001, March, 2001, San Antonio, Tex.

[0047] [4] K. R. Elliot, “High speed HBT Circuitry for Digital SignalSynthesis in Digital Beam Forming Applications”, GOMAC-2001, March,2001, San Antonio, Tex.

[0048] [5] Erik Lier, Dan Purdy, “Techniques to Maximize TrafficCapacity in Multi-beam Satellite Active Phased Array Antennas forNonuniform Traffic Model”, IEEE Phase Array Systems and TechnologyConference, May 2000, Dana Pt. Calif.

[0049] [Sa] E. Lier, A. Jacomb-Hood “Multibeam Active Phased Arrays forCommunications Satelites” IEEE Microwave Magazine, December 2000, pages40-47.

[0050] [6] U.S. Pat. No. 5,943,010, Rudish, et al., Aug. 24, 1999,Direct Digital Synthesizer Driven Phased Array Antenna.

[0051] [6a] U.S. Pat. No. 5,764,187 Rudish, et al. Jun. 9, 1998, DirectDigital Synthesizer Driven Phased Array Antenna.

[0052] [7] U.S. Pat. No. 6,081,226 Caldwell, et al. Jun. 27, 2000,Multi-mode Radar Exciter.

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[0054] [9] U.S. Pat. No. 6,078,629 Critchlow, et al. Jun. 20, 2000,Digital Synthesizer

What is claimed is:
 1. A multiple simultaneous beam system comprising: abeam modulation and pointing computer having an input and an output,user defined modulation control signals for controlling each of 1-M RFbeams being operatively connected to the input of said beam modulationand pointing computer, said beam modulation and pointing computeroperating to convert the user defined user defined modulation controlsignals to a set of digital control signals for controlling the 1-M RFbeams; and a multibeam digitally scanned antenna array apparatusoperatively connected at its input to the output of said beam modulationand pointing computer and operatively connected at its output to 1-Nradiating elements comprising an antenna array so as to simultaneouslygenerate corresponding ones of said 1-M RF beams.
 2. The multiplesimultaneous beam system of claim 1, wherein said multibeam digitallyscanned antenna array apparatus comprises: a multibeam formingsynthesizer having an input and an output, said set of digital controlsignals from said beam modulation and pointing computer beingoperatively connected to the input of said multibeam formingsynthesizer; and 1-N direct digital synthesizers each being operativelyconnected at its input to the output of said multibeam formingsynthesizer, and each being connected at its output to correspondingones of said 1-N radiating elements, such that a single one of said 1-Ndirect digital synthesizers drives a single one of said 1-N radiatingelements to simultaneously generate said corresponding ones of said 1-MRF beams, thereby reducing the number of direct digital synthesizersneeded to transmit said information to be transmitted on each of said1-M RF beams.
 3. The multiple simultaneous beam system of claim 1,wherein said multibeam digitally scanned antenna array apparatus furthercomprises 1-N amplifiers each being operatively connected at its inputto the output of corresponding ones of said 1-N direct-digitalsynthesizers, and each of said 1-N amplifiers being operativelyconnected at its output to corresponding ones of said 1-N radiatingelements:
 4. The multibeam digitally scanned antenna array apparatus ofclaim 2, wherein each one of said 1-N direct digital synthesizerscomprises: a phase accumulator having an input and an output, the inputof said phase accumulator being operatively connected to the output ofsaid multibeam forming synthesizer; an adder operatively connected atone of its inputs to the output of said phase accumulator andoperatively connected at another of its inputs to the output of saidmultibeam forming synthesizer; a sine/cosine lookup table having aninput and an output, the input of said sine/cosine lockup table beingoperatively connected to the output of said adder; a multiplieroperatively connected at one of its inputs to the output of saidsine/cosine look up table and operatively connected at another of itsinputs to the output of said multibeam forming synthesizer; adigital-to-analog converter having an input and an output, the input ofsaid digital-to-analog converter being operatively connected to theoutput of said multiplier; and a filter having its input operativelyconnected to the output of said digital-to-analog converter and itsoutput operatively connected to said corresponding one of said 1-Nradiating elements.
 5. The multiple simultaneous beam system of claim 1,wherein said user defined modulation control signals are time samplesselected from the group consisting of frequency, modulation information,digital data and pointing directs.
 6. The multiple simultaneous beamsystem of claim 5, wherein said beam modulation and pointing computerconverts said user defined modulation control signals for each of the1-M RF beams, and wherein for the m-th RF beam said modulation controlsignals are defined as amplitude, B_(m), frequency, ω_(m), phase, Φ_(m),and beam pointing, θ_(m).